Cyanotype questions

I am about to try some cyanotypes having restricted myself to salt prints previously. I am wondering;_
1) How archival are cyanotypes? I know that old engineering 'blueprints' have lasted well but I am wondering how long it might be expected to keep a cyano on a wall and still look good. (Ignoring the obvious location/siting of the print into account)
2) In that respect, does toning/staining make any difference to their keeping property or is it purely an aesthetic quality?
3) And when toning/staining I guess that the whole substrate is stained or is it possible to colour only the image?

1. I've had cyanotypes on display in my sunny office for a couple years with no visible fading. I'm told if they fade, put them in a dark place and they will gradually unfade. With old blueprints, the paper usually falls apart before the image does.

Colin, cyanotype is one of the most stable processes around, as long as you protect the paper from alkali conditions and you process them well. (If iron remains in the paper it would be detrimental in the long term; but this is a common handicap of all iron processes...) The very first cyanotypes made by Herschel himself (and Anna Atkins a little later - we are talking about 170 years here!) are still in good shape. It is true that the prints may show a little fading (reversible to some extent) when subjected to very strong / energetic light, but this is not an issue with normal indoor lighting conditions, especially so with UV protective glazing.

In short; don't worry about the longevity of cyanotypes, they're practically as stable as pt/pd prints and particularly much much more stable than untoned salt prints!

BTW, there are various toning methods for cyanotype - it's mostly about the looks, not longevity. In fact, we really don't know the long term effect of toning cyanotypes, but we do know that they can last 170 years untoned. See a couple of toners (and their effects) below:

- Lead acetate: You'll get a (presumably) more robust image (less light fading if it happens...) and a considerably colder blue. No staining of paper base...
- Tannic acid and gallic acid: Brown to warm-neutral color (fully toned: brown, split toned: warm-neutral in the shadows, brown in the hihlights...), no data for longevity. (But remember, tannic / gallic acid toning will convert the image to something similar to iron-gall ink, chemistry-wise, and we know that iron-gall ink isn't particularly friendly to paper...) You may get very little or significant staining of paper base depending on the strength of the toner and the sizing of the paper. Hard-sized papers are affected less, and mild toners (along with short toning times) stain less...

Hope this helps,
Loris.

P.S. If you aren't happy with the color of the straight cyanotype I'd suggest some other process instead of fiddling with it by toning. (Split toned prints are nice though. See one of my split-toned prints here.)

Tannic acid toning seems to be very robust. To test it I stapled a toned cyanotype to the deck railing out back. Cleveland doesn't get much sun, it is true, but after a year it looked as good as new - paper was a bit wrinkled but still strong and of a piece.

The toning only affects the image and doesn't color the paper. However there will still be minute amounts of cyanotype pigment in the 'white' portions of the image and these will turn color with toning. When the pigment is still ultra-pale blue it just 'brightens' the paper - see fabric bluing as another use for prussian blue cyanotype pigment http://en.wikipedia.org/wiki/Bluing_%28fabric%29

I use Bienfang Graphics 360 for alt. process. It is a brilliant white, smooth, but rather thin - sort of like tracing paper. 11x14 is about as large as one would want to make what with having to handle the stuff wet. It drymounts very well. And it is cheap - $10 or so buys 50 sheets of 9x12. Cyanotypes can, and should, be very cheap to make. I have heard the paper has changed recently, I don't have any experience with the new stuff; I should probably buy a pad just to see if it is still suitable for alt process.

Gallic acid toning doesn't form the same compound as iron-gall ink. Iron-gall ink was known to the ancient Greeks and parchment and papyrus documents written with iron-gall ink have survived 2,000+ years. The ink has a bad reputation as a faulty recipe was used for making it in the late 1800's in the USA - with atmospheric moisture it would eat through the paper - the insides of handwritten o's, a's, d's, b's ... fall out of the paper, leaving a hole behind. If you wash the print well after toning to remove excess acid there will be no problem. Washing wasn't something one did to handwritten documents in the 1800's. See http://www.realscience.breckschool.o...onGallInk.html and http://en.wikipedia.org/wiki/Iron_gall_ink

Last edited by Nicholas Lindan; 04-13-2012 at 02:54 PM. Click to view previous post history.

Thank you all for your helpful - and for some - very detailed response. M Stat I have purchased a bottle of Ware's chemistry and look forward to using it as a change from my normal salt prints. Thank you again Loris and Nicholas

I agree with the fact that gallic / tannic acid toned cyanotypes are robust (in terms of light fading), I have numerous tannic acid toned cyanotypes that are still in good shape (color and density) after more than a decade. My concern is the possibility of leaving something alien in the paper, that MAY acidify and damage it in the long term, especially in humid conditions... Papyrus isn't a particularly good example; most of the specimens we have on hands were stored in pretty dry conditions - in Egypt and its structure / mechanical properties is considerably different than what we use now... There's an academic web site about iron-gall ink, it says the specimens should be kept in dry conditions (<70% RH) to inhibit the formation of acid, otherwise you get adverse effects pretty quickly. We often have >=70%RH here in Istanbul in the spring and summer, therefore I don't like the idea anymore... If I want a color which is not possible with cyanotype (or other iron processes I practice), I simply use gum dichromate or casein with extremely lightfast pigments.

The tannic acid I have on my hands (technical grade, pretty uncertain stuff which I bought in an unmarked plastic bag, a rust colored fine powder which takes ages to dissolve) usually stained my papers, and the stain was still present in pure paper base where no coating solution was applied. The severity of the stain was changing from virtually unnoticeable (a very little warming, only noticeable when you observe it next to untreated paper) to clearly noticeable (turning bright white paper base to natural / ecru), depending much on the paper / toning solution strength and toning time... (Edit: Maybe it's mechanical staining, undissolved fine tannic acid particles - of the specimen I have on hands - trapped inside paper fibers???)

Regards,
Loris.

Last edited by Loris Medici; 04-13-2012 at 04:12 PM. Click to view previous post history.
Reason: Added a comment